Rotary expansible drill bits



Feb. 4, 1958 J.YF. MUSE Erm. 2,822,150

- ROTARY EXPANSIBLE DRILL BITS 3 Sheets-Sheet 1 l/lo. 3.

Filed A ril f. A f L p wm@ M .T wl 1% nn? .m IM M Z. 1M. Mv. M u, J 8 Il Feb. 4, 1958 J. F. MUSE ErAL 2,822,150

ROTARY EXPANSIBLE DRILL BITS Filed April 18, 1.955

ma Q Feb. 4, 1958 J, F, MUSE ETAL 2,822,150

ROTARY EXPANSIBLE DRILL BITS Filed April '18 1955 s sheets-sheet s E e. E6. 7

United Sttes ROTARY EXPANSIBLE DRILL BITS John F. Muse, Whittier, and Bernard Kriegel, Los Angoles, Calif., assignors to Baker Oil Tools, Inc., Los Angeles, Calif., a corporation of California Application April 18, 1955, Serial No. 501,888

Claims. (Cl. Z55-76) drilling life, and which can still be retracted substantially completely within the contines of the bit body.

Another object of the invention is to provide a rotary expansible well drilling bit, in which the cutters are expandible hydraulically, the circulating fluid being carried to the lower portions ot the bit to insure the complete .flushing of the drill bit cuttings to the top of the well bore.

A further object of the invention is to provide a rotary expansible well drilling bit embodying cutters pivotally carried by the body of the bit on hinge pins, in which the hinge .pins are relieved of the drilling weight and torque load imposed on the cutters during vthe drilling operation.

Yet another object of the invention is to provide a rotary expansible well drilling bit, in which the useful lite of the main body of the bit is increased considerably.

Still a further object of the invention is to -provide a rotary expansible well drilling bit embodying a tandem arrangement of sets of cutters, to secure the .drilling or enlargement of a well bore to a comparatively large diameter in stages, requiring a single trip into the well bore for the production of the hole to the desired size.

Another object of the invention is to provide a rotary expansible well drilling bit embodying a tandem arrangement of sets of cutters, which sets are angularly displaced with respect to each other to secure the drilling of a full gauge, circular well bore to a comparatively large diameter, the drilling bit being stable in its operation.

A further object of the invention is to provide a rotary expansible well drilling bit embodying a tandem arrangement of sets of cutters, in which the outward expansion of .one set of cutters is availed of `to `assist in the out ward expansion of another set of cutters. More specically, the lower set of cutters is rst and partially expanded and the continued expansion of .this lower set aids Ythe expansion of an upper set of cutters.

This inventionpossessesmany other advantages, and Lhas other objectsl which may be made more clearly apparent Vfrom a consideration of several forms .in which it .may be embodied. These lforms are shownin the drawings accompanying and forming part of thepresent speci- /cation Such forms will now be vdescribed in detail, ttor the purpose of villustrating -the general :principles lof the invention; but `vit is to he understood that such Idetailed description is no t to .be :taken .in a :limiting sense,

tent

2 since the scope of the invention is best delined by the appended claims.

Referring to the drawings:

Figure 1 is a longitudinal section, with parts being disclosed in elevation, .through one forni of rotary expansible drill bit embodying the invention, taken generally along the line 1-.1 on Fig. 3, the lower portion of the ligure actually being turned ninety degrees to the upper portion;

Fig. 2 is an enlarged view similar to Fig. l, disclosing the sets of cutters in expanded position;

Fig. 3 is a cross-.section taken along the line 3--3 on Fig. l;

Fig. 4 is a side elevation of the `drill bit disclosed in Fig. l;

Fig. 5 is a fragmentary longitudinal section, similar to Fig. l, of a modified form of a rotary expansible drilling bit;

Fig. 6 is a view similar to Fig. 5, with the cutters partially expanded;

Fig. 7 is a view similar to Fig. 5, with the cutters in still further expanded positions;

Fig. 8 is a fragmentary side elevation of still .another form or" the invention.

A rotary expansible well drilling bit A is illustrated in the drawings which is capable of :being lowered through a string of vwell casing (not shown) to a point therebelow at which a hole enlarging operation is to be desired, the `well bore being .enlarged or drilled to a substantially greater diameter than the inside diameter of the casing through which the apparatus is moved. rlhe apparatus includes an elongate main body 10 having an upper threaded box 11 to .be .threadedly secured to the lower pin 12 of a drill pipe section B forming part of `a string of drill pipe extending to the top of the well bore, and by means of which the hole enlarging apparatus is rotated. The string of Vdrill pipe also ,acts `as a conduit down through which drilling mud, or the like, can .be pumped for operation on the apparatus, and for vthe purpose of removing the cuttings from the Well bore and flushing them upwardly around the string of drill pipe B to the top of the hole.

The body 16 of .the tool carries a plurality of sets of cutters 13, 14 which are initially disposed in a retracted position to enable the tool to be moved through the well casing, but which can be expanded outwardly to a position for increasing the diameter of `the hole. The upper set of cutters 14 consists .of a pair of members parallel to one another, and which are disposed in elongate slots 15 in the body, on opposite sides of its axis, these slots opening outwardly lin opposite directions with respect to the body. A cutter blade 14 is disposed in each slot, having `a hole 16 therethrough for `the reception of a hinge .pin 17 having its outer vportion 18 threaded for the purposes Vofthreaded .reception in a cornpanion bore 19 extending 4from the outer surface of lthe body to the slot. This bore and the pin have their common axis normal tothe cutter blade 14 and slot l5. The inner portion 20 of the pin extends into the 'hole 16 in the blade in a relatively loose fashion, acting as a n hinge pin or fulcrum for the blade.

The blade 14 itself 'is adapted to occupy a depending position entirely within the contines of the body slot 1S, or it can be swung about vthe axis of its hinge pin .17 so that its lower vportion moves laterally in an outward direction to occupy alposition substantially at right angles to the axis of the bit body. The body slots 15 open outwardly in opposite directions and the cutter blades 14 themselves swing outwardly in opposite directions with respect to each other, the axes ofthe 'hinge pins 3 17 being disposed on opposite sides of the axis of the bit and being substantially parallel to each other.

When each blade 14 has been expanded outwardly to its fullest extent, its upper surface 21 (when in expanded position) will engage an upper abutment member 22 disposed within the upper portion of the body slot 15, and which is suitably secured to the body, as by means of a cap screw 23 extending through the abutment member 22 and threaded into body 10. Plihe lower surface of the upper abutment member 22 may be provided with a hardfacing layer 23, such as a layer of tungsten carbide, to resist any hammering or vibrating action of the blades on the abutment member and to increase the life of the latter.

For a similar reason, an inwardly directed nger 24 of the cutter blade 14 disposed on the opposite side thereof from its cutter portion 25 will engage a lower abutment member 26, which is contained within the body slot 15, and which is secured to the body by means of a cap screw 27 extending through the member and threaded into the body 10. The upper portion of this lower abutment member 26 may have a layer of hardfacing material 28 similar to the layer on the upper abutment member 22, which is engaged by the downwardly facing surface 24a of the finger 24 simultaneously with the engagement of the upper surface 21 of the blade 14 with the upper abutment 22.

The abutment members 22, 26 will resist wear on the body due to the drilling weight being; imposed upon the cutter blades 14 as drilling proceeds. Similarly, to minimize the wearing effect of torque loads on the body, the trailing side a of each body slot 15 may have a longitudinally extending wear plate or member 29 disposed in an outer recess 30 in the body and secured to the latter by a plurality of cap screws 31, the heads 32 of which do not extend into the body slot 15. The inner surface of the wear plate 29 has hardfacing material 33 welded thereto and this surface actual-ly forms a continuation of the trailing side 15a of the slot. The trailing face 14a of the blade 14 will engage the wear plate 29 when the blade has been expanded outwardly to its fullest extent, the torque from the body being transmitted to the blade through the wear plate 29 and its hard'faeing material 33.

As a result of the upper and lower abutment members 22, 26 and the wear plate 29, substantially no wear on the body 10 itself occurs, due to the drilling weight and the torque load. If the abutment members or wear plates evidence excessive wear when the tool has been removed to the top of the hole, they can readily be removed merely f tween the blades 14 and the body 10 does not necessitate L expensive rebuilding or scrapping of the body itself, but merely the replacement of certain comparatively inexpensive parts. The body 10 will, therefore, have a very long eiective life, resulting in substantial economies.

For the purpose of preventing the drilling weight and torque loads from being imposed on each of the hinge pins 17, the latter lits loosely within the hole or bore 16 in each blade 14. Thus, the downward drilling weight imposed by the body 10 on a cutter blade 14 during the drilling operation will be transferred from the body 10, through the upper abutment 22 to the upper surface 21 of the expanded blade, and the reactive force of the formation in an upward direction on the blade will be carried by the upper abutment 22 and also by the lower abutment 26', by virtue of engagement of the linger 24 with the upper end of the latter. The pin 1'7 will be free of the drilling'weight and it will also be free of the torque load, in view of its loose t 'in the body hole 16. The drilling torque is transmitted 'fromthe body 10, through the Wear plate 29, to the rear face 14a of the blade 14, and any angular movement between the body and the blade (which, at the most, will be very slight), does not cause the pin 17 to engage the wall of the hole 16 through the blade, in view of the loose tit of the pin in the blade.

The lower set of cutters 13 is arranged essentially the same as the upper set of cutters 14, except that it is disposed angularly ninety degrees with respect to the upper set. For convenience of illustration, the sets of blades shown in the several longitudinal sections are not angularly displaced, but it is evident that the ninety degree angle of displacement actually exists from a consideration of Vthe side elevation view shown in Fig. 4. The lower set of blades 13 consists of two members, the same as the upper set, the blades being parallel to each other and on opposite sides of the body axis, and being disposed in parallel slots 35, opening outwardly of the body. These blades 13 are also mounted on hinge pins 17 secured to the body and extending loosely into holes 16 in the blades, the pins being disposed substantially at right angles to the blades, with the axes of the pins arranged on opposite sides of the axis of the body of the tool. These lower blades 13 also occupy retracted pendant positions in their respective slots 35 and can be swung outwardly (as described hereinbelow) to their fully expanded positions, in which the upper surface 21 of the lower blade 13 engages an upper abutment member 22 and an inner linger or ear 24 on each blade engages the upper end of a lower abutment member 26. The trailing side wall 35a of each slot also has a wear plate 29 secured thereto, through which the torque load is transmitted from the body 10 to the blade 13 during the drilling operation.

The loose t of the lower hinge pins 17 in the lower blade holes 16 and the cooperation ofthe abutment mem bers 22, 26 and wear plate 2Q therewith will also relieve the lower hinge pins 17 of the drilling weight and the torque load to the same extent as the upper set of pins 17.

As described above, each slot 15, 35 opens outwardly of the body in one direction, to allow the blade therein to swing on its hinge pin 16 between retracted and expanded positions. Each slot 15, 35 may also open outwardly of the body in the opposite direction, but only at its upper and lower portions 36, 37, to prevent drilling mud and the like from packing into the slots 1S, 35, thereby impeding expansion of the blade, or their retraction from an expanded position, or both. It is evident that as the lower cutting portion 2S, 38 of each blade swings outwardly, its upper arm portion 39, moves in an inward direction. Any drilling mud that might be disposed in the upper portion of a slot can be forced by the arm out through the upper rear portion 36 of the slot. If a cutter blade is in its outwardly expanded position and it is to be retracted, then. any drilling mud, or other foreign solid, or solid-like, substances in the lower portion of the slot that might tend to prevent retraction of the blade within the slot can be forced by the blade ina lateral direction and out through the lower rear slot portion 37 of the body.

The sets of blades 13, 14 are actuated between retracted position, in which they are disposed downwardly entirely within the confines of the body slots 35, 15 to expanded positions by means of an operating plunger 41 that has a rack and pinion-like connection with each of the blades. This plunger 41 is disposed coaxial of the body and extends through a coaxial bore 42 in the latter. The lower end 43 of the plunger 41 is slidable in the lower portion of the body 10 below the lower slots 35, whereas the upper portion of the plunger is guided in an enlarged bore or cylinder 44 in the upper end of the body through the agency of an actuating piston 45 to which the upper end of the plunger is threadedly secured. The piston has one or more piston rings 46 mounted thereon for slidably sealing against the wall of the cylinder 44. The plunger 4 1 yitself is tubular, to conduct the fluid pumped down sealed 5 through the drill pipe B and through the plunger 41 into a passage 47 through the lower end of the body.

A pilot or guide member 43 may have an upper pin 49 threaded into a lower box 50 in the body, the uid discharging from the plunger passing into a central passage 51 in the guide, from which it can exit through a plurality of nozzle outlets 52. The drilling mud then passes from lthese outlets upwardly around the tool A to convey any cuttings to the top of the hole. Leakage of uid between the lowpr portion of the plunger 41 and the body 10 may be prevented by a suitable rubber, or rubber-like, seal ring 53, such as an ring, disposed in a groove 54 in the body and engaging the periphery of the plunger or operating rod.

It will be noted that the operating rod 41 extends completely along both the upper and the lower sets of blades 14, 13 and also between the blades of each set. There is an operating connection between the plunger and the blade of each set. Thus, the plunger 41 may have transversely projecting teeth or pins 55, 56 extending from its upper and lower head portions 57, 58 that may be made generally rectangular in crossasection, these teeth or pins being engageable with companion gear teeth or pins 59, 60 formed on the arm portions .39, 40 of the cutter blade 14, 13. For each set of cutters, the teeth or pins 55, 56 project from opposite Sides of the driving head 57, S and engage the arm portion teeth on opposite sides of the cutter blade hinge pins (Fig. 3). As an example, the teeth 55 of the upper head 57 will engage the teeth 59 of one blade 14 on the side of the hinge pin 16 removed from the open end of the slot 1S, and the teeth 57 projecting from the same drive head will also engage the teeth 57 of the other blade 14 of the same set on the side of the other hinge pin 16 remote from the open end of the slot 15. Since the slots open in opposite directions, the interengaging teeth 55, 59 between the plunger 41 and one blade 14 are disposed on the opposite side of the blade hinge pin 15 from the teeth 55, 59 of the plunger and the other blade 14 relative to the piu 15 of such other blade. Accordingly, longitudinal movement of the plunger 41 in one direction will swing the blades 14, 14 in opposite directions. As an example, downward movement of the plunger 41 will swing the lower cutting portion of the blades in an outward and upward direction toward their fully expanded position, and upward movement of the plunger 41 will retract the blades .14, 14 completely within the contines of the body 10 of the tool. Since the lower set of blades 13 is actually disposed at ninety degrees to the upper set of blades 14, the pins or teeth 56 on the lower drive head 58 of the plunger 41 will be disposed at right angles to the teeth or pins on the upper drive head 57.

rIhe operating plunger 41 is moved in a downward direction hydraulically, for'the purpose of expanding the blades 13, 14. To secure the proper hydraulic pressure, y

an orifice member 63 is disposed in the upper portion of the piston 45 and the operating rod or plunger 41. This orice member 63 may be threaded into the upper end of the plunger 41, a retaining nut 64 being threaded into the piston 45 into engagement with a flange 65 secured to the oriiice member, which forces an elastic gasket ring 66 against an internal shoulder 67 in the piston, to prevent leakage around the orice member 63. Fluid pumped down through the drill pipe B will pass through the oriiice member 63, which will cause a back pressure to build up on the upstream side of the piston 45 and plunger 41, forcing these members downwardly against the force of a helical compression spring 68 surrounding the plunger, with its lower end engaging the lower end 69 of the cylinder 44 and its upper end engaging the piston 45. Some of the uid can, of course, pass through the oriiice member 63, to proceed down thro-ugh the 'plunger 41 into the lower portion 47 of the body, discharging through the pilot nozzles 52.

AThe fluid under pressure will shift the rod 4i downwardly, and through the pin and teeth connections 55, S9 and 56, 60 swing the lower portions 25, 38 of the blades 14, 13 in an upward and outward direction to the fullest extent, determined by engagement of the upper sides 21 of the blades with the upper abutment member 22 and the inner blade lingers 24 with the lower abutment members 26. In the event that the iuid pressure is relieved, then the retracting spring 6i; will tend to elevate the piston 45 and operating plunger 41, to cause the teeth 55, 56 on the plunger heads 57, 58 to engage the opposite sides of the blade teeth 59, 60, swinging the blade arms 39, 40 upwardly and their cutter portions 25, 38 in a downward and inward direction entirely within the confines of the tool body 10.

In the use of the apparatus A, it is lowered in the well bore with the blades 13, 14 in retracted position, and the piston 45 and operating plunger 41 in their upper position. The apparatus is lowered through the well casing to the point below the casing shoe (not shown) at which the hole enlarging operation is to commence. The hole enlarging operation is performed in stages, the lower set of blades 13 being shorter than the upper set of blades l14, so that the lower set 13 will increase the diameter of the original well bore to an intermediate size, whereupon the upper set of blades 14 will remove additional formation material from the wall of the well bore to increase the diameter of the hole to a greater extent.

When the drilling operation is to commence, the drill pipe B and drill bit A attached thereto are rotated at the proper speed and drilling mud, or similar drilling fluid, is pumped down the drill pipe. This uid will pass through the plunger 41 and out through the lower nozzles 521, proceeding back to the top of the well bore around the drill bit and the drill pipe. A liuid pressure will be built up on the upstream side of the piston 45, forcing it and the plunger 41 downwardly against the force of the spring 68, causing the rack and pinion interconnections between the plunger and the various blades to swing the blades 13, 14 outwardly, the lower ends of the blades iirst engaging the wall of the well bore. Rotation of the apparatus continues, without longitudinally moving the drill bit A, the blades 13, 14 progressively digging away into the wall of the well bore and being expanded outwardly to a greater extent until they ocr cupy their fully expanded positions, such as shown in Fig. 2, in which the lower set of blades 13 engage their respective abutment members 22, 24, which is also true of the upper set of blades 14. The lower set of blades 13 will then have produced a tranverse formation shoulder D in the well bore that extends from the wall of the initial hole C 'to the greater diameter size hole E being produced by the lower set of blades. The upper set of blades 14 will have their outer ends projecting laterally outward to a substantially greater extent than the lower set of blades, the lower cutting edges of these blades then being capable or" operating upon a formation shoulder F that will extend between the wall of the intermediate size hole E and the wall of the nal diameter hole G produced by the upper set of blades.

The necessary drilling weight can now be imposed on the drill pipe B, body 10 of the tool A and the cutters 13, 14, this drilling weight causing the cutters to drill away the formation material by acting upon the shoulder D, F. The lluid being pumped through the app-aratus is actually no longer necessary to retain the cutters 13, 14 in their expanded positions, since the drilling weight itself insures their retention in an outward position. However, the circulation of the drilling mud preferably continues, so that it will pass through the operating plunger 41 and be discharged through the lower outlet nozzle 52, in order to comingle with the cuttings and carry them back to the top of the well bore. During the drilling operation, the drilling weight and torque loads are not being imposed upon the hinge pins 16 themselves, in view of the abutting relationship between the upper sides 21 of the blades with the upper abutment members 22 and of the blade lingers 24 with the lower abutment members 26. Also, the drilling of a concentric bore is insured, inasmuch as the blades are making contact with the Wall of the well bore at four angularly displaced points therearound. Actually, the blades are displaced about ninety degrees from each other, and, in view of their mounting in the slots and on the body, the cutting edges possess a negative rake, which is conducive to smoother operation of the drill bit.

In view of the tandem relationship between the upper and lower sets of cutters 13, 14, assurance is had that a full gauge hole will be drilled. The cuttings are completely removed by the circulating fluid. Should there be any tendency for the cuttings to remain in the region of the lower blades 13, there might be some irregularity in their cutting action on the formation, and such blades may not produce a uniform bore hole size. However, the upper set of blades 14 cannot have any cuttings interfering with them, since such cuttings: would drop down away from the shoulder F toward the lower set of blades. As a result, the upper set of blades 14 will not be operating on any mass of previous cuttings, but will be acting upon open, undisturbed formation at all times, insuring the smooth operation of the upper set of cutter blades and the drilling of a full gauge concentric hole.

After the cutters have become worn, or the hole has been enlarged along the desired length, the cutters are to be retracted, to enable the apparatus to be withdrawn through the well casing to the top of the wall bore. It is merely necessary to relieve the pressure of the drilling fluid in the drill pipe by ceasing the pumping action of fluid through the apparatus, whereupon the spring 68 will elevate the piston 45 and plunger 41, causing the teeth or pins 55, 56 on the plunger to engage the blade teeth 59, 60 swinging the arms 39, 40 upwardly and the blades 13, 14 back into the confines of the well body 10. In the event that the blades do not retract completely within the confines of the body, the elevation of the tool through the casing shoe causes the outer surfaces of the blades to engage the latter, which will then force them into the body slots 15, 35, the blades elevating the plunger 41 to its upper position. The apparatus can now be withdrawn through the well casing.

In the form of apparatus disclosed in Figs. 1 to 4, inclusive, the upper and lower sets of blades 14, 13 are expanded outwardly simultaneously from the very beginnlng. When operating in comparatively hard formation,

the upper blades 14, being longer than the lower blades 13, offer greater resista-nce to outward expansion than the lower blades, in view of the slighter angle at which they initially contact the wall of the well bore. Accordingly, greater pressures or a greater extent of time is required to secure full expansion of both sets of blades 13, 14. In the form of invention disclosed in Figs. 5 to 7, the outward expansion of the blades is facilitated by causing the lower set of blades 13 to partake of an initial expansion before the upper set 14 begins expanding. Accordingly, the full hydraulic force acting on the piston 45 and plunger 41 is effective to cause the lower set of blades to dig into the wall of the well bore and produce a shoulder D therein. After the partial shoulder is secured, then the lower blades 13 can be availed of to facilitate expansion of the upper set of blades 14.

To accomplish the aforenoted objective, the pins or teeth 56 on the lower head 58 engage the teeth 60 of the lower blades 13 substantially at the outset of the downward movement of the plunger 41, so that the initial downward movement of the latter is effective to swing the lower blades 13 outwardly toward their expanded position. However, the initial movement of the plunger 41 is not effective to swing the upper set of blades 14 outwardly. This is due to the provision of a certain amount drive head 57 and the teeth 59a of the upper blades 14, which will require that the plunger 41 move downwardly to a certain extent before the upper head teeth 55 and blade teeth 59a coengage, as is evident from an inspection of Fig. 5. Accordingly, during the rotation of the apparatus and the pumping of liuid therethrough to expand the blades outwardly, the lower set of blades 13- is first expanded outwardly against the wall of the well bore to a partial extent and will form a partial transverse shoulder ltherein capable of supporting these blades and i'esisting their downward movement (Fig. 6). Thereafter, as the piston 45 and plunger 41 are moved downward hydraulically to a further extent, the upper plunger teeth 5S will come into engagement with the teeth 59a of the upper set of blades 14, swinging the latter outwardly against the formation. lf there is any substantial resistance to these blades producing their shoulder F in the wall of the well bore, such resistance can be overcome by the combination of the hydraulic fluid acting downwardly on the piston 45 and plunger 41 and by imposing drilling weight ou the drill pipe B and the body 10 of the tool. Such drilling weight will be incapable of moving the tool downwardly, inasmuch as the lower set of blades 13 are supported by the formation shoulder 14. Such downward movement will shift the body 10 in a downward direction, causing the lower blades 13 to pivot on their hinge pins 16 and press the downwardly facing surfaces of their teeth 60 in a downward direction upon the lower plunger teeth 56, to shift the plunger 41 downwardly. This downward movement of the plunger will cause it to expand the upper blades 14 against the wall of the well bore with a much greater force than is supplied by the hydraulic lluid itself acting on the piston and plunger.

As a matter of fact, after the partial shoulder 14 has been formed by the lower blades 13, their complete expansion, as well as the outward expansion of the upper set of blades 14, can occur merely by rotating the apparatus while imposing a certain amount of drilling weight on the lower set of blades, the lower set acting through the plunger 41 to expand the upper set of blades 14.

After the lower set of blades 13 has been expanded outwardly to its fullest extent, as determined by engagement of each of the lower blades with the abutment members 22, 26, the upper set of blades 14 will not have been expanded outwardly to its fullest extent into engagement with such abutment members (see Fig. 7). The plunger 41 cannot move downwardly to any further extent. However, there then exists a lost motion space between each of the rack teeth 55 on the upper driving head 57 and the downwardly facing side of the upper blade teeth 59a, that will allow the downweight imposed by the drill pipe B on the body 10 of the tool and on the upper set of blades 14 to swing the upper set of blades upwardly to their fullest extent and into contact with the several abutment members 22, 26 (broken line condition on Fig. 7). In moving to such an extent, the downwardly facing teeth surfaces will again move toward a position of adjacency with respect to the upper head driving teeth 55.

The apparatus disclosed in Figs. 5 to 7 is operated in the same manner as in the previously described form of the invention, and is elective to enlarge the wall of the well bore in two stages. When the tool is to be retrieved from the hole, the pumping of fluid therethrough is discontinued, the spring 68 elevating the piston 45 and operating rod 41, causing the pins on the latter to engage the blade teeth and swing both sets of blades 13, 14 back to retracted positions. If the blades are not retracted completely within the contines of the body 10, then their engagement with the casing shoe, as a result of elevation of the apparatus in the well bore, will force the blades 13, 14 completely inwardly.

In the form of invention disclosed in Fig. 8 an upper blade and plunger portion is disclosed for use in the arrangement disclosed in Figs. 5 to 7. Provision is made for expanding the lower set of blades 13 outwardly to a partial extent, and for then commencing the expansion of the upper set of blades 14, th: upper set of blades Vbeing expanded to their fullest extent by the operating plunger 41 itself, instead of only to a partial extent, as in Fig. 7. T accomplish this objective, a predetermined amount of lost motion is provided between the driving teeth 55 of the upper head 57 of the plunger 41 and the blade teeth 591) therebelow. However, the upper head teeth 55 are disposed closer to the axes of the hinge pins 16 for the blades 14 than the driving teeth 56 to the axes of the hinge pins for the lower blades 13. Accordingly, during the downward movement of the plunger 41 within the body to expand the blades 13, 14 the lower plunger teeth 56 will engage the lower blade teeth 66 and expand the lower blades 13 outwardly to a certain extent, so that the full hydraulic force is available for forming the lower formation shoulder H to a partial extent. When the plunger 41 has moved downward surliciently to engage the upper plunger teeth 55 with the upper blade teeth 5%, the upper blades 14 will swing outwardly, but to a greater angular vextent than the lower set of blades 13 are then moved, inasmuch as the upper teeth 55 engage the upper blade teeth 59b at a smaller radius from the pivot axis of each blade 14. Accordingly, as the plunger 4i continues to move downwardly, the upper set of blades 14 will be swung outwardly by the plunger 41 to the fullest extent at the same time as the lower set of blades 13 reach their maximum expanded position.

During the retraction of the upper set of blades 14, they will both reach their fully retracted position under the action of the plunger itself at substantially the same time, being retracted to the same extent. Elevation of the plunger 41 will initially produce a retracting movement of the lower set of blades 13, but not of the upper set, because of the initial lost motion between the teeth 55, 5917. The latter will not begin retracting under the actionof the operating plunger until the upper plunger teeth 55 catch up to and engage the upper blade teeth 5%. When such engagement occurs, continued upward lmovement of the plunger will shift the upper blades 14 inwardly toward a fully retracted position. Since these teeth 55 are closer to the pivot axis of each blade 14 than the teeth 56 of the lower head 5d are to each pivot axis of a lower blade, the linear movement of the plunger 41 will produce a greater angular retracting movement of the Lipper blades 14 than the lower blades 13, the upper blades arriving at their fully retracted position at the same time as the lower set of blades, which will be when the plunger has been elevated substantially to its fullest extent.

Accordingly, it is evident that the plunger 41, in the form of invention shown in Fig. 8, is effective to move the lower set of blades 13 out to a partial extent before the upper set of blades 1d commences expanding, while still being capable of expanding both sets of blades positively to their fullest extent, which, in the speciiic torni of invention disclosed is substantially ninety degrees. Accordingly, the lower set of blades 13 is acted on hydraulically irst to insure the availability of the full hydraulic force in producing its partial shoulder H. The hydraulic force is then available to expand both sets of blades outwardly simultaneously. l-f any substantial resistance to outward expansion is encountered, then the imposition of drilling weight on the lower set of blades 13 will cause the lower set of blades to shift the plunger 41 downwardly, and thereby facilitate the full outward expansion of the upper set oi' blades 14 by supplementing the hydraulic `force on the piston 45 and plunger il supplied by the drilling liuid.

The inventors claim:

l. I-n a rotary expansible drill bit for well bores: a main body connectible to a drill string; upper and lower sets of cutters pivotally mounted on said body and occupying initial retracted positions in said body; the upper set of cutters being substantially angularly displaced with respect to the lower set of cutters to the extent that the cutters of said upper set are substantially uniformly spaced circumferentially of said body :from the cutters of said lower set; and means movable longitudinally within said body and operatively connected to said -sets of cutters for substantially simultaneously expanding said sets of cutters outwardly.

2. In a rotary expansible drill bit for well bores: a main body -connectible toa drill string; upper and lower sets of cutters pivotally mounted on said body and occupying initial retracted positions in said body; the upper set of cutters being substantially angularly displaced with respect to the lower set of cutters to the extent that the cutters of said upper set are substantially uniformly spaced circumferentially of said body from the cutters of said lower set; a plunger slidable longitudinally in said body; and a rack and pinion connection between said plunger and sets of cutters for expanding said sets of cutters outwardly.

3. In a rrotary expansible drill bit for well bores: a main body connectible to a drill string; upper and lower sets of cutters pivotally mounted on said body and occupying initial retracted positions in said body; the upper set of cutters being substantially angularly displaced with respect to the lower set of cutters; a tubular plunger slidable longitudinally in said body and adapted to discharge drilling iluid received from the string at the lower portion of said body; a rack and pinion connection between said plunger and sets of cutters; a-nd a piston secured to said plunger subject to the pressure of uid in the drill string for yshifting said plunger in said body and expanding said sets of cutters outwardly.

4. In a rotary expansible drill bit for well bores: a main ybody connectible to a drill string; upper and lower sets of cutters pivotally mounted on said body and occupying initial retracted positions in said body; the upper set of cutters being substantially angularly displaced with respect to the lower set of cutters to the extent that the cutters of said upper set are substantially uniformly spaced circumferentially of said body from the cutters of said lower set; and means movable longitudinally within said body and operatively connected to said sets of cutters for substantially simultaneously expanding said sets of cutters outwardly; said upper set of cutters having a greater elect'ive hole drilling diameter than said lower set of cutters.

5. In a rotary expansible drill bit for well bores: a main body connectible to a drill string and having a .plurality of non-radial slots therein; cutter means pivotally mounted on said body and disposed in said slots; an operating plunger movable longitudinally in said body between and along the sides of said slots and cutter means; an operating connection between said plunger and cutter means; and means for shifting said plunger longitudinally of said body to expand said cutter means laterally outward of said slots.

6. In a rotary expansible drill bit for well bores: a main body connectible to a drill string and having a plurality of non-radial slots therein; cutter means pivotally mounted on said body and disposed in said slots; an operating 'plunger movable longitudinally in said body between and along 'the sides of said slots and cutter means; a rack and pinion connection between said plunger and cutting means; and means for shifting said plunger longitudinally of said body to expand said cutter means laterally outward of said slots.

7. In a rotary expansible kdrill bit for well bores: a main body connectible to a drill string and having a plurality of non-radial slots therein; cutter means pivotally mounted on said body and disposed in said slots; an operating plunger movable longitudinally in said body between and along the sides of said slots and cutter means; an operating connection between said plunger and cutter means; means for shifting said plunger longitudinally of said body to expand said cutter means laterally outward of said slots; an upper abutment in the upper end of each slot removably secured to said body and engaged by said cutter means when in fully expanded position; a lower labutment member in each slot removably secured to said body and engaged by said cutter means when in fully expanded position; and a wear plate removably secured to said body in the trailing side of each slot and engaging the trailing side of said cutter means to transmit torque load `from said body to said cutter means.

8. In a rotary expansible drill bit for well bores: a main body connectible to a drill string and having a pair of parallel slots therein disposed on opposite sides of the longitudinal axis of the body and opening laterally outward of said body in opposite directions; a cutter blade in each slot pivotally mounted on said body; an operating plunger movable longitudinally in said body between and along the sides of said slots and cutter blades; an operating connection -between said plunger and cutter blades to swing said blades in opposite directions in said slots; and means for shifting said plunger longitudinally of said body to expand said cutter blades laterally outward of said slots in opposite directions.

9. ln a rotary expansible drill bit for well bores: a main body connectible to a drill string and having a pair of parallel slots therein disposed on opposite sides of the longitudinal axis of the body and opening laterally outward of said body in opposite directions; a cutter blade in each -slot pivotally mounted on said body; an operating plunger movable longitudinally in said body between and along the sides of said slots and cutter blades; a rack and pinion connection between said plunger and each cutter blade to swing said blades in opposite directions in said slots; and means for shifting said plunger longitudinally of said body to expand said cutter blades laterally outward of said slots in opposite directions.

l0. In a rotary expansible drill bit for well bores: a main body connectible to a drill stringand having a plurality of non-radial slots therein; hinge pins secured to said body and extending transversely into said slots; a cutter blade in each slot having a bore receiving a hinge pin; the diameter of said bore being substantially greater than the diameter of said hinge pin; an operating plunger movable longitudinally in said body between and along the sides of said slots and cutter means; an` operating connection between said plunger and cutter means; means for shifting said plunger longitudinally of said body to expand said cutter means laterally outward of said slots; an inner abutment member in the upper end off each slot removably secured to said body and engaged by said cutter blade when in fully expanded position; a lower abutment member in each slot removably secured to said body and engaged by said cutter means when in fully expanded position; and a wear plate removably secured to said body in the trailingr side of each slot and engaging the trailing side of the cutter blade in said slot to transmit torque loads from said body to said cutter blade.

ll. In a rotary expansible drill bit for well bores: a main body connectible to a drill string; upper and lower sets of cutters pivotally mounted on said body and occupying initial retracted positions in said body; and means movable longitudinally of said body and operatively connected to said sets of cutters for rst expanding said 12 lower set of cutters and then expanding said upper set of cutters. y

l2. In a rotary expansible drill bit for well'bores: a main body connectible to a drill string; upper and lower sets of cutters pivotally mounted on said body and occupying initial retracted positions in said body; a plunger slidable longitudinally in said body; an operating connection between said plunger and lower set of cutters for expanding said lower set of cutters outwardly; and an operating lost motion connection between said plunger and upper set of cutters -tor expanding said upper set of cutters outwardly; said lower set of cutters being expanded outwardly upon longitudinal movement of said plunger prior to outward expansion of said upper set of cutters.

13. ln a rotary expansible drill bit for well bores: a main body connectible to a drill string; upper and lower sets of cutters pivotally mounted on said body and occupying initial retracted positions in said body; a plunger slidable longitudinally in said body; a lower rack and pinion connection between Isaid plunger and each cutter of said lower set; an upper rack and pinion connection between said plunger and each cutter of said upper set; the teeth of said upper rack and pinion being initially out of engagement and engaging after longitudinal movement of said plunger has expanded said lower set of cutters partially outward.

14. In a rotary expansible drill bit for well bores: a main body connectible to Ia d-rill string; upper and lower sets of cutters pivotally mounted on said body and occupying initial retracted positions in said body; a plunger slidable longitudinally in said body; a lower rack and pinion connection between said plunger and each cutter of said lower set; an upper rack and pinion connection between said plunger and each cutter of said upper set; the teeth of said upper rack and pinion being initially out of engagement and engaging after longitudinal movement of said plunger has expanded said lower set of cutters partially outward; the teeth of said upper rack engaging said upper pinion teeth closer to the pivotal axis of each upper cutter than the point of engagement of said lower rack and pinion teeth to the pivot axis of each lower cutter.

l5. In a rotary expansible drill bit for well bores: a main body connectible to a drill string; upper and lower sets of cutters pivotally mounted on said body and occupying initial retracted positions in said body; a plunger slidable longitudinally in said body; an operative connection between said plunger and cutters of said lower set for swinging said cutters of said lower set outwardly upon longitudinal movement of said plunger in said body; and an operative connection between said plunger and cutters of said upper set for swinging said upper cutters outwardly at a greater angular rate than said lower cutters upon longitudinal movement of said plunger in said body.

References Cited in the le of this patent UNITED STATES PATENTS 1,478,306 Sweetman Dec. 18, 1923 2,495,509 Cressey Ian. 24, 1950 2,654,575 Kammerer Oct. 6, 1953 2,679,383 Garrison May 25, 1954 2,754,090 Kammerer July l0, 1956 

